Apparatus for firing or sintering fine material

ABSTRACT

The apparatus comprises a firing or sintering chamber followed by a fine material separator. Material from a fine material preheater and air form an air preheater are introduced into a premixing chamber, A connection is provided for introducing a mixture of preheated fine material and air from the premixing chamber into the firing or sintering chamber, and fuel is introduced in a flow which is substantialby coaxial with the flow of air and fine material, to cause the fuel to burn in the air and to heat the fine material.

iinited States Patent Ritzmann 1 July 11%, R973 APPARATUS FOR FIRING 0R SINTERING 2,689,973 9 1954 Lee et al 34 10 x FINE MATERIAL [75] Inventor: got-st Ritzmann, Neubeckum, Primary Examiner john J. Camby ermany Assistant Examiner-Henry C. Yuen {73] Assignee: Polysius AG, Neubeckum, Germany & Yeasting 22 Filed: Sept. 9, 1971 21 A l. N .1 178 901 l 1 PP 57] ABSTRACT Foreign Application Priority Data The apparatus comprises a firing or sintering chamber 1970 Germany P 20 61 9801 followed by a fine material separator. Material from a fine material preheater and air form an air preheater [52] US. Cl 432158, 34/10, 34/57 R, are introduced into a premixing chamber, A connec- 4 tion is provided for introducing a mixture of preheated [51] Int. Cl. F27b 9/38 fine material and air from the premixing chamber into [53] Field Of Sea 263/21 21 32 the firing or sintering chamber, and fuel is introduced 263/33 57 57 A in a flow which is substantialby coaxial with the flow of air and fine material, to cause the fuel to burn in the air [56] References Cited and to heat the fine material.

UNITED STATES PATENTS 3,603,568 9/1971 Ritzmann 263/21 R 3 Claims, 1 Drawing Figure The invention relates to an apparatus for firing and- /or sintering of fine material, with an arrangement for preheating the fine material, a firing or sintering zone supplied with fuel, a fine material separator as well as a cooling apparatus, in which the firing or sintering zone is preceded by a mixing zone for the mixing of the preheated fine material with the preheated combustion air. An apparatus of this general type is shown in U.S. Pat. No. 3,603,568 of Sept. 7, l97l. An apparatus of the type described in US. Pat. No. 3,603,568 is distinguished by relatively low cost of construction and by the absence of moving parts, while making possible the attainment of a high throughput capacity, as compared with other known types of apparatus. Specifically, when the preheated fine material is mixed with the preheated combustion air, before these two components are brought into the firing zone with the fuel, then it is assured that the fine material will enter the zone of highest temperature and thus will be subjected to an intensive heat treatment, which makes possible the completion of the firing or sintering operation in a fraction of a second.

The invention then has for its object to provide an improved embodiment of the apparatus hereinbefore described which retains its advantages and which de fines still more exactly the motion and therefore the heat treatment of the fine material in the firing zone.

In accordance with the invention, this object is achieved in that the flow of the mixture of fine material and combustion air into the firing or sintering zone is substantially coaxial with the flow of the fuel into the zone.

In this way it is assured that each individual particle of the fine material must travel through the flame. As a result it is guaranteed that a particle of material which is located outside of the space occupied by the flame already has been subjected to the necessary high temperature heat treatment. in this space outside of the flame, therefore, desired processing operations can be performed (particularly for cooling and/or separating of the fine material) without incurring the danger of thereby including also particles which have not yet been subjected to any sufficient heat treatment.

Extensive tests on which the present invention is based have shown that in accordance with the invention when the flow of the mixture of fine material and combustion air is concentric with the flow of fuel an exact pass of each preheated particle of fine material through the zone of the flame is guaranteed, and a fraction of a second suffices for the heat transfer. In this way, a very compact, simply constructed apparatus of high throughput capacity is achieved.

The drawing is a diagrammatic elevation of an apparatus embodying the invention.

In general, the illustrated apparatus comprises for example a two-stage preheater l, a substantially horizontally arranged firing apparatus 2 below the preheater, and a cooler 3 which may likewise consist of two stages. The preheater 1 is composed of two cyclone separators 4- and 5 arranged one above the other, wherein the exhaust gas duct 6 of the cyclone separator 5 is connected to the inlet opening of the cyclone separator 4, and the material discharge duct 7 of the cyclone separator 4 is connected to the gas inlet duct 8 of the cyclone separa tor 5.

By means of a duct 9, the material outlet of the cyclone separator 5 is connected to a mixing duct 11, into which discharges also a duct 12 ending in a nozzle 1l2a, which comes from the cooler 3 and supplies preheated combustion air. The mixing duct ll extends into a firing chamber 13 and is surrounded by a casing 14 which is connected to a fuel supply duct 15 and discharges through an annular nozzle 16. In this way, the flow of the mixture of fine material with combustion air is substantially coaxial with the flow of the fuel into the firing or sintering zone, since in the illustrated embodiment the inlet (mixing duct 11) for the mixture of fine material and combustion air is arranged concentrically with the inlet for the fuel (casing 14 with annular nozzle 16).

The firing or sintering chamber 13 is composed of a tube which is provided at one end with the hereinbefore described inlets for the fuel and the mixture of fine material and combustion air, and at the other end leads into a fine material separator 17 which is in the form of a cyclone separator. The clip pipe 17a of this cyclone separator is connected to the duct 8, while the material discharge duct i8 leads into a duct 19 which connects the dip pipe of one cooling cyclone separator 20 with the gas inlet of the other cooling cyclone separator 21. The dip pipe of this cooling cyclone separator 2i. is connected to the hereinbefore described duct 12, while the material discharge duct 22 of this cyclone separator 21 discharges into the fresh air duct 23 which leads to the cyclone separator 20.

The operation of the apparatus is then as follows:

The fine material which is to be fired 0r sintered is preheated in the two-stage preheater l by means of the exhaust gases from the firing or sintering zone which flow through the duct 8. The supply of the material thus enters the duct 6 (arrow 24); after separation in the cyclone separator 4, the fine material (arrow 25) travels into the cyclone separator 5, from which it is supplied through the duct 9 to the mixing duct 11. There it is intimately mixed with the combustion air which is being discharged at high velocity from the nozzle 12a, and which constitutes the exhaust from the cooler 3 (arrow 26). The mixture of fine material and combustion air comes into contact with the fuel (arrow 27) in the vicinity of the annular nozzle 26. The fine material therefore must travel through the flame zone 28, which is indicated by a dashed line, before it enters the separator 17. The fine material and the flaming gases flow through the tubular firing or sintering chamber substantially in concurrent flow. After separation in the separator E7, the fine material (arrow 29) travels into the cooler 3, in which it is cooled in two stages by means of the fresh air (arrow 30).

The illustrated embodiment may be modified in various ways within the scope of the invention.

For example, it is not absolutely necessary that the flow of the fuel and the mixture of fine material and combustion air be discharged into the firing or sintering zone in a substantially horizontal direction. Indeed, a vertical arrangement is possible, in which these flows are directed downward. in this case, of course, a somewhat modified construction of the separator which is connected to the firing or sintering zone is necessary.

Other modifications are possible within the scope of the invention in which instead of having the fine material separator directly connected to the firing or sintering zone, for example, it can be connected by means of a tangential duct, or the firing or sintering zone itself may constitute a fine material separator or a part thereof.

lt will be understood further, with regard to the structure of the coaxial inlets for the fuel and the mixture of fine material and combustion air that a great number of possibilities exist, which are known for example in the burner art. Thus a great variety of round or annular nozzles can be used; and one of the two components may flow radially inward.

I claim:

1. Apparatus for firing or sintering fine material, comprising a tubular firing or sintering chamber having an inlet end, and having its opposite end connected to a fine material separator, an air preheater, a fine material preheater, a premixing chamber and means for introducing material from the fine material preheater and air from the air preheater into the premixing chamber, wherein the improvement comprises a feed nozzle leading from the premixing chamber into the inlet end of the tubular chamber, and an annular burner nozzle which is connected to a fuel supply and is coaxial with and surrounds the feed nozzle to cause the fine material from the feed nozzle to enter coaxially the flame produced by the burner nozzle 2. Apparatus according to claim 1, wherein the nozzles for introducing fuel, fine material and air into the firing or sintering chamber discharge into the chamber in a substantially horizontal direction.

3. Apparatus according to claim 1, wherein the fine material separator is directly connected to the firing or sintering chamber. 

1. Apparatus for firing or sintering fine material, comprising a tubular firing or sintering chamber having an inlet end, and having its opposite end connected to a fine material separator, an air preheater, a fine material preheater, a premixing chamber and means for introducing material from the fine material preheater and air from the air preheater into the premixing chamber, wherein the improvement comprises a feed nozzle leading from the premixing chamber into the inlet end of the tubular chamber, and an annular burner nozzle which is connected to a fuel supply and is coaxial with and surrounds the feed nozzle to cause the fine material from the feed nozzle to enter coaxially the flame produced by the burner nozzle.
 2. Apparatus according to claim 1, wherein the nozzles for introducing fuel, fine material and air into the firing or sintering chamber discharge into the chamber in a substantially horizontal direction.
 3. Apparatus according to claim 1, wherein the fine material separator is directly connected to the firing or sintering chamber. 